Multi-state switching systems



Sept. 25, 1962 L. s. oNYsHKEvYcH ETAL 3,056,039

MULTI-STATE SWITCHING SYSTEMS Filed Oct. '7, 1958 3 Shee'liS-Sheei'l 2ign 5. wf/y .94. i@ IN VENTORS LUBDMYR S. DNYSHKEWCH t WALTER EKnsnuncxv 5r WMP/Vif Sept. 25, 1962 s. oNYsHKEvYcH ETAL 3,056,039

MULTI-STATE SWITCHING SYSTEMS 11M -ffff'f INVENTORS LUBDMYR S. NYSHKEWCH5 WALTER E Knsnnncxy United States Patent 3,056,039 MULTI-STATESWITCHING SYSTEMS Lubornyr S. Onyshkevych, Princeton, and Waiter F.Kosonocky, Newark, N I assiguors to Radio Corporation of America, acorporation of Delaware Filed Oct. 7, 1958, Ser. No. 765,888 9 Claims.(Cl. 307-88) This invention relates to switching systems, andparticularly to switching systems using multi-state logic circuits.

Switching systems involve the interconnection of a plurality ofmulti-state elements to perform a logical operation on two or more inputsignals. The most commonly used element is a two-state element, such asa magnetic core, a flip-flop circuit, or an electronic gating circuit.In switching systems using two-state elements, the switching functioncan be expressed in a two-state logical algebra called Boolean algebra.Other multi-state logical algebras are known, for example, a three-statealgebra called Post algebra. Most three-state logical circuits arerelatively complex or are marginal in operation and, therefore, areseldom used. One problem with prior art three-state logic circuits isthat the output signals corresponding to the three stable states are notsuiciently distinct; another problem is that the margin of response todifferent combinations of input signals is too narrow for reliableoperation.

It is an object of the present invention to provide improved three-statelogic circuits.

Another object of the present invention is to provide improved switchingsystems using multi-state logic circuits.

Still another object of the present invention is to provide improvedswitching systems using three-state logic circuits which are relativelysimple in construction and reliable in operation.

According to the present invention, a parametric oscillator circuit isused as a three-state logic circuit. The circuit is operated to providethree distinct outputs each controlled by a different combination ofinput signals. The circuit exhibits a wide margin of response to thedifferent combinations of input signals. One output is represented b-yoscillations of one phase, another by oscillations in the phase oppositethe one phase, and the third output is represented by the absence ofoscillations.

A feature of the invention involves the use of the parametric oscillatorcircuits to obtain directivity of information flow in a switching systemusing a single A.C. supply source.

In the accompanying drawings:

FIG. l is a generalized block diagram of a parametric oscillator circuituseful in the prese-nt invention;

FIG. 2 is a schematic diagram of a parametric circuit using variablecapacity diodes;

FIG. 3 is a schematic diagram of a parametric circuit usingferromagnetic cores;

FIG. 4 is a graph of the the output of the circuit voltage;

FIG. 5 is a timing diagram plaining the operation of the vention;

FIGS. 6 and 7 are each a graph of the response characteristic of theoutput of the circuit of FIG. l as a function of control voltage whenoperated in the regions II and III, respectively, of FIG. 4; and

FIGS. 8 through 16 are each block diagrams of dilferent multi-statelogical system according to the present invention.

A parametric oscillator system includes a non-linear reactance elementconnected with a linear reactance in a response characteristic of ofFIG. 1 as a function of supply of waveforms useful in excircuits of thepresent in- 3,056,039 Patented Sept. 25, 1962 tuned circuit. Frequently,a pair of non-linear reactances, such as the non-linear reactances 20and 22 of FIG. 1 are connected in a balanced circuit arrangement to thelinear reactance 24. The balanced arrangement operates to prevent thesupply frequency of an A.C. (alternating current) supply source 26 fromreaching an output device 28. The circuits are tuned to resonate at amultiple of the supply frequency. The present circuits are tuned to thesecond sub-harmonic (the frequency f) of the supply frequency (2 f)because the energy conversion between the supply and output isrelatively high at the second sub-harmonic frequency. Also, as describedmore fully hereinafter, the tristable operating region is mostpronounced at the second sub-harmonic frequency. Other multiples of thesupply may ybe chosen if necessary,

so on.

The phases in which the oscillations occur are controlled by signalssupplied by a control source 30. The oscillations lock into the phase ofthe control signals. After the oscillations are locked in the desiredphase, the control signals can be removed and the phase of theoscillations remains unaltered. Two phases are of interest in thepresent invention. These two phases are mutually opposite each other,and hereinafter are designated the A signal and the B signal. Assuming astandard control signal of frequency (f), the A signal is in phase withthe standard signal, and the B signal is out of phase with the standardsignal. The A and B signals, then correspond to two separate informationsignals. The control source 30 is used to set the oscillator to eitherone of the phases corresponding to the A and B signals.

In FIG. 2, the non-linear reactances are provided by a pair of variablecapacity crystal diodes 20 and 22. The diodes 20' and 22' exhibit anon-linear capacity when biased in the reverse direction by any suitablebias source, such as the batteries are junction diodes cheap and arereadily available. Other variable capacity diodes such as point contactdiodes may be used. The variable capacity reactance elements can beprovidas the grid-cathode capacitance of a pentode type vacuum tube, bycondensers having dielectrics of ferroelectric material, and so on. Alinear inductance element 24 provides the linear reactance. Atransformer 27 couples the A.C. supply source 26 to the parametriccircuits. The primary winding of the transformer 27 is connected to thesupply source 26. The secondary winding of the transformer 27 has acenter-tap connected to the ungrounded end terminal of the inductance24. The end terminals of the secondary winding are connected to thecathode and anode respectively of the diodes 20' and 22 to provide apair of halanced tuned circuits. The control source 30 and the outputdevice 28 are each connected to the ungrounded end terminal of theinductance 24'.

In FIG. 3, the non-linear reactances lare provided by a pair of cores 20and 22 of ferromagnetic material. A suitable magnetic material is oneexhibit-ing a rectangular hysteresis characteristic. The A.C. supplysource 26 is coupled to the cores r2.0 yand 22 by 'a pair of supplywindings 36 and 38 `linked in the Isame lone sense to the cores 20 and22 respectively. The ycores 20 and 22 Aare Ibiased to 'a suitable pointon their characteristic by 'any suitable bias rneans, not shown. Thelinear reaotance is provided by a linear capacitor 24 -coupled to a pairof output windings 40 yand 42 of the cores 20 and 22, respectively. The`output windings 40, `ft2 are linked in Imutually `opposite `senses 'tothe cores 20, 22". Control relatively signa-ls are supplied to theoscillator circuits via a resistance element 44 connected across thecapacitor 24".

Each or the parametric oscillator cir-cuits eiectively is la twoter-minal device, hence the response of each oscillator circuit issymmetrical with respect to signals appearing at the input land outputterminals. Thus, the input and output terminals can be interchanged witheach other in each of the circuits of FIGS. 1, 2, and 3 without changingthe circuit operation. Also, the principle of superposition applies, anda plurality of sepanate input signals may be coupled to the same inputpoint, with the resulting net input signal controlling the circuitoperation.

In operation, the parametric oscillator circuit exhibits three distinctregions i t response to increasing A.C. supply voltage from the A.C.source 26. These three regions of the parametric circuit of FIG. 2 areindicated by the response characteristic 50* of FIG. 4. FIihe curve 50is 'a plot of the output voltage `amplitude at frequency (f) vs. thesupply voltage amplitude tor la .given tuning and given supplyirequency. In region I, between the points o and a, the circuit does notoscillare. Substantially no output voltage is: produced because thesubaharrnonic trequency (f) is not generated, and because the circuitsare assumed to be periectly balanced, the supply frequency (2 j)completely cancels in the output circuit. In region II, lbetween thepoints c and d of the supply voltage, the circuit is always oscillating,and :further may be oscillating in either one or the other of the twophases.

Region III ol the curve 60 is va tristable region. That is, the circuitmay be (1) not oscillating, (2) oscillating in one phase, or (3)oscillating in the opposite phase. In the prior tart, the region II istreated :as ya transition region, and the circuit operation is carriedout in either region I or region II. The desired phase in which thecircuit oscillates is controlled by whether an A phase control signal ora B phase control signal was applied during the build-up of theoscillations. lIn the prior art, the control signal is 'applied prior tothe application of the supply signals. The later applied supply signalsthen cause the circuit to oscillate in the desired phase. The controlsignals then rnay be removed and the circuit continues to oper-ate in :a`desired phase so long as the supply signals are present.

The operation of a parametric oscillator circuit is indicated by thewaveforms of FIG. 5. In line f the solid and dotted wavetorms 62 land 64respectively represent the A and the B phase control signals. Thewaveform 66 of line g represents the supply signals, and the solid anddotted Iwaveforms 66 and `68 of line h represent the output waveformscorresponding to the A and B phase control signals, respectively. Fromthe curves of FIG. 5, it is seen that between the times t and t1, priorto 'the application of the supply signals, the circuit is notoscillating `and no, or at most relatively small amplitude outputsignals, due to :transformer coupling of the control signals, areproduced. Between the times t1 and t2, after the supply signal isapplied, the oscillations begin to buildup in amplitude until la maximumlamplitude is reached at a later time t3. Thereafter, the circuitoscillates at .the maximum amplitude. The control signals may be removedat any time between the times t1 and t3 after the oscillations havestarted to build-up.

The response characteristics of the output voltage of a parametriccircuit as 'a function of control signal yamplitude when operating inregion II (the bistable region), is shown by the curve 70 of FIG. 6. Theupper portion of the curve 70 represents one phase of output signals,Iand the lower por-tion of the curve 70 represents, the other phaseoutput signals. In FIG. 6, it is assumed that a supply voltage ofsufficient amplitude, say S1 of FIG. 4, is applied at the time t1 ofFIG. 5. As shown by the curve 70, the circuit exhibits a relativelynarrow regio-n 71 of uncertainty with respect to phase of theoscillations. rIlhus, .in the absence ot previously applied contr-olsig- A nais, the phase in which the oscillations will occur isunpredictable. It is because of this phase uncertainty that the priorart parametric devices apply the control signal prior to the supplysignal. Logical gating operations are per-termed in the prior artdevices by linear addition of the control signals (a Kirchhoi lawaddition) betere the supply voltage is applied to the circuit.

The curve 74 of FIG. 7 represents acteristic of the parametric circuitof FIG. 1 as a tnnction of control signal amplitude when the circuit isoperated in the tristable region III (FIG. 4). Thus, Afor a ixed supplyvoltage of S2 volts (FIG. 4), a relatively large threshold to controlsignal Iamplitude (FIG. 7) exists. `Contro-1 signals in encess yof {V3}volts must be applied before the circuit beg-ins oscillation. Thisrelatively large control signal threshold, not `found in the bistableregion, permits novel logical switching operations. The switchingsignals do not have to be yapplied before the supply signals to controlthe output phase. Thus, a net control signal of amplitude smaller thanthe critical ampltiude lV3l does not produce parametric oscillations,while a net control signal larger than W31 always produces oscillationsin the desired phase.

The switching circuit of FIG. 8 is la ternary logic circuit using aparametric oscillator circu't of FIGS. 1, 2 or 3. Higher speed operationcan be obtained with the circ-uit of FIG. 2 than can be obtained withthe circuit of FIG. 3 because the magnetic elements tend to heat-up atthe higher frequencies. A pair ot three-value control signals C land Dare used to control the output of the gat-ing circuit 80. 'Ihe y'absenceof la control signal C or D corresponds to a ternary "0; the presence ofa control signal in the A phase corresponds to a ternary 1; and thepresence of a control signal in the B phase corresponds to la ternary 2signal. When present, the C and D control signals yare of -amplitude V3(FIG. 7). The output rfunction lgenerated by the ternary circuit of FIG.8 is :given in map form. in the table of FIG. 9. For ease oiillustration, the table of FIG. 9 designates the ternary l A signal bynumerical value 1, and the ternary 2 B signal by ia +1, land the ternary0 signal by a 01. Each of the other tables referred to hereinafter usesa similar designation. The nine (311) possible outputs `generated by thenine possible combinations ot the C and D control signals of the gatingcircuit 80` are shown in FIG. 9.

The gating circuit 82 of FIG. 10 corresponds to la ternary coincidencecircuit in which both the ternary control inputs C and D are eachrestricted to an amplitude (FIG. 7.) Thus, both C and D inputs of thesame ternary Value must be present at the saine time betore an outputsignal is produced. 'Ilhe table of FIG. 111 expresses the nine (3)possible outputs produced vfor all the nine possible combinations of Cand D control signais.

Other ou-tput functions may be obtained by using an additional biasinput signal of one phase and of a given amplitude, For example, thecircuit 84 of FIG. 12 uses a full amplitude bias signal in the B phasein conjunction with full amplitude C ,and D control signals to generatethe output function shown in the table ot FIG. 13.

The switching circuit ot' FIG. 14 uses .a half-amplitude bias signal inthe B phase in conjunction with half-amplitude C and D control signalsto generate the output function shown in the table of FIG. 15. Any ofthe output functions may be inverted by using a transformer to take theoutput signals from the switching circuit. In such case, the signs ofthe l signals in each of the squares of the tables are reversed fromthat shown in the drawing.

The parametric gating circuits according to the inventhe responsechartion also may be operated in a manner to provide directivity to theow of information signals through a plurality of cascaded parametriclogic circuits. The prior parametric circuits obtained directivity ofinformation ow by using a plurality of separate A.C. supply sources andmodulating these separate supply sources in a given fashion. In FIG. 16,a plurality of parametric switching circuits 12 are interconnected inthree levels for performing various logical operations on separatecontrol input signals E through L The system of FIG. 16 is shown as .ageneralized system because the particular logic `functions performed bythe system would vary depending upon the use `of the system in aparticular switching network. A single A.C. supply source 94 is coupledto each of the switching circuits. The supply signals from the source 94have ian amplitude of S2 (FIG. 4) volts such that each of the switchingcircuits is normally not oscillating.

The first level switching circuits 83 :are controlled by the inputcontrol signals E through 1. The output functions of the ih'st switchingcircuits can be any logical function such as that expressed in lthetables of FIGS. 9, ll, 13, or l5. The outputs of Ithe iirst levelswitching circuits 88 control the second level of switching circuits 99.Again the functions generated by any of the second level switchingcircuits 90 can be set to generate various output functions. The outputsignals of the second level of switching circuits 90 control the thirdlevel of switching `circuits 92 in similar fashion to provide the finaloutput signals.

In operation, all the logic functions of the interconnected switchingcircuits are performed without interrupting or modulation of the A.C.supply. Also, the directivity of information flow is assured since (1)each of the switching .circuits operates as a separate coincidencecircuit, and (2) the signals appearing on an input iine of one switchingcircuit `due to the oscillation of that one circuit are of insuiicientamplitude to change the state of any preceding switching circuit.

There have been described herein improved multistate switching circuitsusing parametric oscillators. These circuits provide a relatively largethreshold for coincident type operations, and provide -distinct outputsignals for each of the separate states. "[ihe circuits may beinterconnected in various fashions in Iswitching systems to providecomplex switching functions using a common A.C. supply source.

What is claimed is:

1. A switching system comprising a parametric oscillator circuit, saidcircuit having an operating region in which A.C. supply signals areinsufcient in amplitude to cause oscillations, [and in which controlsignals above a given amplitude cause ci-rcuit oscillations joint-lywith said A.C. signals, the phase of said circuit oscillations beingcontrolled by said control signals, and means for applying said controlsignals selectively to said circuit to initiate desired oscillations.

2. A ternary logic circuit comprising a parametric oscillator circuithaving an operating region in which the circuit oscillations are jointlycontrolled `by the A.C'. supply and by a control signal above ya minimumamplitude, and means to `apply said control signal to said oscillatorcircuit, the ternary values of said log-ic circuit correspondingrespectively to the absence of oscillations, to oscillations in onephase, and to oscillations in a phase different from the one phase.

3.` A switching system comprising :a parametric oscillator circuit, saidcircuit having a hysteresis region over a given range of A.C. supplyvoltage in which the circuit exhibits a relatively large threshold tooscillation initiating control signals, and in which the circuit remainsoscillating `after the removal of said control signals, means forapplying A.C. signals Within said range to said circuit, and means forapplying selectively two or more control signals to said circuit, saidcontrol signals 6 when applied initiating oscillations only when saidthreshold is exceeded.

4. A switching system comprising a parametric oscillator circuitresponding to `an A.C. signal having a selected operating frequencydifferently in accordance with the dierence in a characteristic of saidA.C. signal, said characteristic being one of -frequency and amplitude,said circuit fbeing non-oscillating in ya first region of saidcharacteristic, being oscillating in a second region of saidcharacteristic, and, in a third region of said characteristic, betweensaid other two, the said circuit remaining oscillating if it isoscillating and remaining non-oscillating if it is non-oscillating,means to Iapply said A.C. signals with -a characteristic limited to saidthird region, `'and means lfor applying a control signal to said circuitto initiate oscillations.

5. A switching system comprising fa parametric oscillator circuit, saidcircuit having a hysteresis region over a given range of A.C. supplysignals in which the circuit exhibits a relatively large Ithreshold tooscillation initiating control signals, and in which the circuit remainsoscillating after the removal of said control signals, means forapplying A.C. signals within said range to said circuit, means forapplying to said circuit a bias control signal having an amplitude atleast equal to said threshold and of one phase, `and means for applyingto said circuit a plurality of control signals each having an amplitudeequal to that of said bias control signal 4and each of said controlsignals being of either said one phase or of the opposite phase, saidcontrol signals when applied initiating oscillations in said oppositephase when both said control signals are present in the opposite phaseand said control signals when present initiating oscillations in saidone phase when at least one of said control signals is present in saidone phase.

6. A switching system comprising 4a parametric oscillator circuit, saidcircuit having a hysteresis region over a given range of A.C. supplysignals in which the circuit exhibits a relatively large threshold tooscillation initiating control signals, and in which the circuit remainsoscillating -after the rem-oval of said control signals, means forapplying A.C. signals within said range to said circuit, means forapplying to said circuit a bias control signal having an amplitude lessthan said threshold Value and of one phase, `and means for applying tosaid circuit a plurality of other control signals each having anamplitude less than said threshold value and each being of either saidone phase or of the phase lop-posite the said one phase, said othercontrol signals initiating oscilations when and only when the netcontrol signal applied to `said circuit is in excess of said thresholdvalue.

7. A switching system comprising rst and second parametric oscillatorcircuits, each of said circuits having a hysteresis region over a givenrange of A.C. supply signals in which region the circuit exhibits arelatively large threshold to oscillation initiating control signals,and in which region the circuit remains oscillating after the removal ofsaid control signals, said circuits each having van output and an input,means coupling the output of said first circuit to the input of saidsecond circuit, means for applying A.C. signals within said range toboth said first and second circuits, means for applying selectively twoor more control signals to said first circuit, 4said control signalswhen applied initiating oscillations in said first circuit when and onlywhen said first `circuit threshold is exceeded, and means for applyingto said second circuit a further control signal, said further controlsignal with said rst circuit output jointly initiating oscillations insaid second circuit when and only when said second cicuit threshold isexceeded.

8. A switching system comprising `a plurality of groups of parametricoscillator circuits, each of said circuits having -a plurality ofcontrol inputs and 'an output, means interconnecting said groups ofcircuits in multi-level logical grouping by connecting the respectiveoutputs of a first of said groups to the inputs of one or more of saidcircuits of a second of said groups yand so on, an A.C. supply sourcefor applying A C. supply signals to yall said oscillator circuits, saidA.C. supply signals being of an amplitude insuicient to produce circuitoscillations, and means to apply selectively to the said circuits ofsaid iirst group a plurality of control signals, said con-trol signalswhen applied jointly with said A.C. signals causing said first group oflogic circuits to oscillate in phases determined by :the 'phases of said`applied control signals, said lsecond group of logic circuitsoscillating in a phase determined by the phase of the control signalsapplied from said outputs of said first group of logical circuits, andso on.

9. A switching system comprising a plurality of parametric oscillatorcircuits arranged in `a switching system, means for applying at the sametime A.C. supply signals to each of said oscillator circuits of anamplitude insufficient to produce circuit oscillations, and means toapply selectively at least first and second control sig- 8 nals to eachof said oscillator circuits, sai-d first and second control `signalswhen applied jointly Wit-h said A.C. signals, causing said circuitreceiving the said control signals to oscillate when both said rst andsecond con trol signals are in the samev one phase, and said controlsignals not causing said circuit receiving said control signals tooscillate when said control signals are applied in mutually oppositephases.

References Cited in the le of this patent UNITED STATES PATENTS OTHERREFERENCES Elementary Principle of Parametron for Datamation, vol. 4,No. 5, Sept-Oct. 1958, pages 31-34.

